Poster abstract

We report the results of the first deep, wide-field, near-infrared methane imaging survey of the Rho Ophiuchi cloud core to search for T dwarfs. Among the 6587 objects detected, 22 were identified as T dwarf candidates. Brown dwarf models indicate that at the age and distance of the Rho Ophiuchi cloud, these T dwarf candidates have masses between 1 and 2 Jupiter masses. If confirmed as genuine T dwarfs, these objects would be the youngest, lowest mass, and lowest gravity free-floating objects ever directly observed. The existence of these candidates suggests that the initial mass function of the Rho Ophiuchi cloud extends well into the regime of planetary mass objects (planemos), and lends support to the possibility that planemos can form via the same process as that for stars. On theoretical grounds, there is some critical mass and density below which cloud fragmentation and gravitational collapse is not feasible. In this context, it is highly suggestive that none of our 22 planemo candidates (and none of 9 more planemo candidates in the CrA cloud identified by us using the same methods) have spectral types later than T6, despite the fact that our surveys are sensitive to spectral types as late as T8. A large fraction (59\% $\pm$ 16\%) of our T dwarf candidates appear to be surrounded by circumstellar disks, and thus represent the lowest mass objects yet found to harbor circumstellar disks.